The former California congressman has been written off by political insiders. He has pennies in his coffers compared with the leading candidates. And his positions on the issues popular with primary voters aren't appreciably different from those of the five other GOP candidates.

But in recent weeks, Riggs' campaign has gathered buzz with a testosterone-heavy approach.

A recent campaign ad, dubbed "Clear Choice," shows a shirtless Riggs doing pull-ups while wearing a backward Army baseball cap. He unfurled the endorsement of ­faded rocker and right-wing pot-stirrer Ted Nugent. And he's taken on a more combative tone in forums, chiding state Treasurer Doug Ducey during last Monday's debate for saying he opposes Medicaid expansion when he did nothing to fight it at the time.

"I thought I'd show everybody the in-person metaphor of the strong governor I'd be," Riggs said last week when asked by The Arizona Republic editorial board about the "Clear Choice" ad.

Still, some observers say a higher and more-macho profile won't be enough to deliver a Riggs victory.

As of June 30, Riggs had a smaller war chest than any Republican or Democratic candidate other than Andrew Thomas. Christine Jones raised more than $2.2 million. Doug Ducey secured more than $1.6 million for the primary and roughly another $400,000 in a general-election fund, and both candidates were supported by independent expenditure groups. Riggs' total fundraising is $213,724, nearly all of that his own money.

"It makes it impossible to mount any sort of serious campaign if you're not raising well into the six figures," said Robbie Sherwood, executive director of the ­non-profit government-transparency organization ProgressNow Arizona.

"Mostly what his campaign is going to be doing ... is showing up at forums and getting his turn to speak in front of audiences and maybe traveling around meeting voters face to face," Sherwood said. "But in a primary that includes this many candidates with well-resourced campaigns, he's not going to come close to winning."

Riggs recently found money to send a mailer and air the "Clear Choice" ad.

He said he does not listen to the polls or the doubters and argues he has already set himself apart from the crowded field. The other campaigns, he says, are merely stealing his message. "It's kind of like the old joke goes: 'I know I can beat them. I just don't know if I can beat me,' " he said.

Yet since the influx of children crossing the border focused the race on immigration, Riggs has sounded a similar message to his opponents, saying he would enforce immigration laws and provide additional law-enforcement resources to help secure the border. His oft-repeated promise to "stop the 'Obamanization' of Arizona," also sounds similar to the ­other Republican candidates' vows to fight federal hegemony.

As he campaigns, Riggs does contrast his position on charter schools and his pledge to roll back Medicaid with the rest of the GOP field.

Riggs, who calls Arizona his "adopted state," looked right at home at a recent campaign event at a Macayo's Mexican Restaurant in Phoenix. Riggs was there to receive the endorsement of the Association of American Physicians and Surgeons. The group approved of Riggs' opposition to Gov. Jan Brewer's decision to expand Medicaid.

Riggs sported a shiny "Frank Riggs for Arizona Governor" name tag and a striped tie. Amid the smell of steaming meat and the sound of crackling tortilla chips, he listened to about 35 doctors, health-care professionals and state legislators give their opinions on Medicaid and the Affordable Care Act.

"If you ask two questions at the mic, you have to double your donations to Frank Riggs. If you ask three, it's triple," joked Dr. Michael Robb, a neurologist and the night's emcee.

When it was Riggs' turn to take the floor, he told the group that he intends to downsize Medicaid by tightening eligibility and removing able-bodied, childless adults from the health-insurance program for poorer Arizonans. He wants them to find work and receive health insurance through health savings accounts.

Dr. Jane Orient, an internal-medicine practitioner and the executive director of AAPS, said she plans to vote for Riggs. "We oppose the Medicaid expansion in Arizona, and that is probably what drew our attention to Frank's campaign," she said.

Orient said she also supports his border-security plan, calling illegal immigration and detainment prime opportunities for infectious diseases.

Riggs also has the endorsements of former Republican presidential candidate Rick Santorum and former state Sen. Russell Pearce, who both back his voting record on religion, abortion, taxes and guns.

As he does at every campaign stop, Riggs reminded the audience of his strong record: three-term congressman from California, veteran, ex-police officer, influential advocate for the charter-school movement.

"I'm certainly happy to put my record alongside the record of contribution and accomplishments of my opponents," Riggs said.

Education is a cornerstone of his campaign and has been the thrust of his work since 1998 when he was the lead author of the federal Charter Schools Expansion Act. Since then, he worked for a non-profit, securing financing for charter schools, and now works for a for-profit charter-school consulting firm — work that he says is on hold during the campaign.

Riggs cited the controversial Common Core program, known in the state as Arizona's College and Career Ready Standards, as his first major target if elected, promising to repeal it and to ask for the resignation of officials who voted for it.

He continued to speak to AAPS until Orient signaled his time was up with the wave of a yellow notepad. His right hand punctuated one last point.

He had garnered some votes from the crowd, and said he feels confident that he's building enough momentum to make a surge. "I've never been one to buy the odds," Riggs said.